33,679 research outputs found
A Preliminary Check-List of the Marine Algae of the Moss Landing Jetty: An Annotated Floristic Compilation. Annual Report, Part 7, 1973
(PDF contains 55 pages
A non-invasive measure of minerals and electrolytes in tissue
A system for collecting epithelial cells from the oral mucosa for the determination of ion concentration is discussed with application to the study of man's adaptation to microgravity. A number of characteristics of these cells influenced the choice for clinical testing. They are non-cornified epithelial cells located on the inferior aspect of the tongue; therefore, they are well protected from trauma. They have the capability of reflecting relatively recent physiologic changes since they are renewed every three days and have aerobic metabolism. Most importantly, they are easily accessible and can be removed by a wooden applicator stick with minimum discomfort. Smears of cells removed in this manner show predominantly individual cells rather than sheets of contiuous cells. This facilitates the visual isolation of single cells with the electron microscope for analysis. NASA's principle effort in the development of a test to measure the ion concentration in sublingual cells has been research by the biomedical program carried out by scientists with expertise in skeletal metabolism. These efforts were directed toward determining the biological meaning and deviations in interacellular ions in nonhuman primates and in male volunteers for experiments in a model for weightlessness. A brief one page summary of the experiments and results are presented
Skeletal responses to spaceflight
The role of gravity in the determination of bone structure is elucidated by observations in adult humans and juvenile animals during spaceflight. The primary response of bone tissue to microgravity is at the interface of the mineral and matrix in the process of biomineralization. This response is manifested by demineralization or retarded growth in some regions of the skeleton and hypermineralization in others. The most pronounced effects are seen in the heelbone and skull, the most distally located bones relative to the heart. Ground based flight simulation models that focus on changes in bone structure at the molecular, organ, and whole body levels are described and compared to flight results. On Earth, the morphologic and compositional changes in the unloaded bones are very similar to changes during flight; however, the ground based changes appear to be more transient. In addition, a redistribution of bone mineral in gravity-dependent bones occurs both in space and during head down positioning on Earth. Longitudinal data provided considerable information on the influence of endocrine and muscular changes on bone structure after unloading
Sustainable agricultural development strategies in fragile lands:
Current trends in demography, agricultural production and rural environment in the developing countries suggest that so-called "marginal lands" must play a larger and probably growing role in food supply and economic development for the foreseeable future. To fulfill this critical role, public policy towards these lands needs to be revised. A key policy focus should be to strengthen incentives for local land users to not only maintain, but to improve the natural resource base for food and fiber supply. Such "land-improving investments" are needed to reduce production and subsistence risks and permit more intensive use without degradation. Under population and market pressure, one can expect an endogenous process of intensification, through land improvements, tenurial and institutional changes and "re-ordering" of the landscape. But this process is not automatic. Factors influencing the pace and scale of land transformation include: farmer knowledge of degradation of the degrading resource; incentives for long-term investment; capacity to mobilize resources for land investment; level of economic returns to such investment; and factors affecting the formation and function of local groups to help mobilize resources and coordinate landscape-level change. Current policies often work to constrain, rather than support, this process. New research is needed to support policy change for "marginal" lands.Land use Economic aspects., Investments.,
Absorption Systems In Radio-Selected QSO Surveys
Radio-selected samples of quasars with complete optical identifications offer
an ideal dataset with which to investigate dust bias associated with
intervening absorption systems. Here, we review our work on the Complete
Optical and Radio Absorption Line System (CORALS) survey whose aim is to
quantify this bias and assess the impact of dust on absorber statistics. First,
we review previously published results on the number density and gas content of
high column density absorbers over the redshift range 0.6 < z < 3.5. We then
present the latest results from CORALS which focus on measuring the metal
content of our unbiased absorber sample and an investigation of their
optical--IR colours. Overall we find that although dust is unarguably present
in absorption galaxies, the level appears to be low enough that the statistics
of previous magnitude limited samples have not been severely affected and that
the subsequent reddening of background QSOs is small.Comment: Proceedings of IAUC199, Probing Galaxies through Quasar Absorption
Lines, P. R. Williams, C. Shu, and B. Menard, ed
Differential forms, Fukaya algebras, and Gromov-Witten axioms
Consider the differential forms on a Lagrangian submanifold . Following ideas of Fukaya-Oh-Ohta-Ono, we construct a family of
cyclic unital curved structures on parameterized by the
cohomology of relative to The family of structures
satisfies properties analogous to the axioms of Gromov-Witten theory. Our
construction is canonical up to pseudoisotopy. We work in the
situation that moduli spaces are regular and boundary evaluation maps are
submersions, and thus we do not use the theory of the virtual fundamental
class.Comment: 51 pages, 6 figures; improved exposition, added illustrations,
corrected minor errors, added reference
Planning for Pedestrians and Bicyclists in North Carolina.
Over the past decade, as obesity has continued to rise among both youth and adults, interest has grown in developing policies to promote community environments that support healthy lifestyles.1 A broad range of local, regional, state, and federal policies under the rubrics of active living, smart growth, and sustainable development share the underlying assumption that they can help people make healthier choices. From a transportation planning perspective, the benefits of pedestrian and bicycle plans resulting from the building of infrastructure to support pedestrian and bicycle travel include improved health (for example, through increased levels of physical activity and reduced obesity), a better environment (for example, through lower carbon emissions), and a stronger economy (for example, through lower fuel bills). However, until more recently, the health benefits have not been specifically explored
Oracle Inequalities and Optimal Inference under Group Sparsity
We consider the problem of estimating a sparse linear regression vector
under a gaussian noise model, for the purpose of both prediction and
model selection. We assume that prior knowledge is available on the sparsity
pattern, namely the set of variables is partitioned into prescribed groups,
only few of which are relevant in the estimation process. This group sparsity
assumption suggests us to consider the Group Lasso method as a means to
estimate . We establish oracle inequalities for the prediction and
estimation errors of this estimator. These bounds hold under a
restricted eigenvalue condition on the design matrix. Under a stronger
coherence condition, we derive bounds for the estimation error for mixed
-norms with . When , this result implies
that a threshold version of the Group Lasso estimator selects the sparsity
pattern of with high probability. Next, we prove that the rate of
convergence of our upper bounds is optimal in a minimax sense, up to a
logarithmic factor, for all estimators over a class of group sparse vectors.
Furthermore, we establish lower bounds for the prediction and
estimation errors of the usual Lasso estimator. Using this result, we
demonstrate that the Group Lasso can achieve an improvement in the prediction
and estimation properties as compared to the Lasso.Comment: 37 page
Innovative and marketing strategies of the Starbucks company in the middle eastern region during uncertainty
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